Cleaning compositions which include an abrasive component are well known. Typically, these abrasive cleansers are used in the cleaning, or scouring, of hard surfaces.
Abrasive cleansers must be formulated such that the abrasive, such as calcium carbonate, is stably suspended therein. In the formulation of such cleansers, attempts to suspend the abrasive stably have often resulted in rheological problems, for example, an unacceptable increase in thickening over time, and/or syneresis problems, whereby the solids portion and the liquids portion of the composition separate over time. When such abrasive compositions include a bleach component, attempts to suspend the abrasive stably have often resulted in an additional problem of bleach instability.
Thickened aqueous cleaning compositions which include a bleach and stably suspend abrasives have been developed. See Choy et al., U.S. Pat. Nos. 4,599,186 (issued Jul. 8, 1986), 4,657,692 (issued Apr. 14, 1987), and 4,695,394 (issued Sep. 22, 1987) and Argo et al., U.S. Pat. No. 5,346,641 (issued Sep. 13, 1994). For example, Choy et al. teach abrasive, bleach-containing, hard-surface cleansers in which an inorganic colloid thickener, namely, alumina, is combined with a surfactant/electrolyte system to provide good physical stability. Further by way of example, Argo et al. disclose an abrasive, hard-surface cleanser which includes an alumina thickener, a surfactant for providing desirable rheological properties and cleaning, an electrolyte/buffer, a halogen bleach, a particulate abrasive, and a viscosity-stabilizing amount of a multivalent salt. The abrasive, hard-surface cleanser of Argo et al. provides good abrasive suspension capability and viscosity stability and exhibits plastic flow. Plastic flow is often desirable in a thickened cleaning composition, so that, for example, shearing of the composition is not required to promote fluidity appropriate for use.
Abrasive-free cleaning compositions are generally more easy to formulate than abrasive cleansers, as the burden of stably suspending an abrasive and the problems associated therewith are removed. Abrasive-free cleaning compositions and methods associated therewith are subjects of the present invention.
Liquid or gel detergent cleaning compositions which include gelling or stabilizing agents, but do not include abrasives or bleach, are known. See Begs et al., Vista Chemical Company, International Publication No. WO 94/16808 (Published Aug. 4, 1994); and Dyet et al., The Procter & Gamble Company, International Publication No. WO 94/05758 (Published Mar. 17, 1994). For example, Begs et al. disclose an alumina-thickened detergent composition which contains a gelling agent. In the Begs et al. composition, the alumina is present in an amount sufficient to render the composition thixotropic, while the gelling agent is said to flocculate the alumina or to cause the alumina to gel. The thixotropic character of the Begs et al. composition differs significantly from the plastic flow character (above) desirable in a thickened cleaning composition.
Further by way of example, Dyet et al. disclose a liquid or gel detergent composition which includes non-ionic surfactant, anionic sulfate and/or anionic sulfonate surfactant, calcium and/or strontium ions, and a stabilizing agent selected from malic acid, maleic acid and/or acetic acid. Dyet et al. describe calcium as being useful in a detergent composition containing polyhydroxy fatty acid amide for the cleaning of greasy soils. However, calcium is known to be difficult to formulate into a stable liquid composition. Dyet et al. thus employ stabilizing agents, namely, malic, maleic, and/or acetic acid, which are needed to stabilize the calcium or strontium ions of their composition. While Dyet et al. disclose these acids as being useful stabilizing agents in their bleach-free composition, such acids would have a detrimental effect on bleach stability in a composition employing a bleach component such as, for example, a halogen bleach.
Ahmed et al. disclose a thixotropic, aqueous, liquid automatic dishwashing detergent composition which may contain a bleach component. See Ahmed et al., U.S. Pat. Nos. 4,970,016 (issued Nov. 13, 1990) and 5,089,161 (issued Feb. 18, 1992). In addition to a bleach component, Ahmed et al.'s detergent composition includes a thixotropic thickener and an anti-filming agent of alumina or titanium dioxide. The thixotropic thickener may be an organic fatty acid or fatty acid polyvalent metal salt and/or an inorganic colloid-forming clay material. The anti-filming component of the Ahmed et al. composition is said to reduce filming on dishware and glassware in dishwashing applications. As the Ahmed et al. composition is thixotropic, it does not exhibit the plastic flow character desirable in a thickened cleaning composition.
There remains a need for an abrasive-free, thickened aqueous cleaning composition, including a bleach and a colloidal thickener, which has desirable viscosity, plastic flow, phase stability and bleach stability.